A. Field of the Invention
The present invention relates to bags which are used in existing automatic filling processes, and more particularly to a novel bag construction which permits the automatic filling of material such as feed or the like into a polypropylene bag.
In automatic bag filling processes, it is known to arrange a plurality of closed bags in a horizontal stack and then open a top bag by means of a suction device. The bag is then moved into a vertically open position for placement underneath a filling spout. Paper bags have been commonly used in such automatic filling processes, but the use of air pervious polypropylene bags has been heretofore impractical because a suction force applied to a bag surface will also be transmitted to the other side causing both sides to lift. The opening of a horizontally stacked polypropylene bag is thus prevented.
The present invention provides a polypropylene bag which may be used in existing automatic bag filling processes. The bag of the present invention includes spaced-apart notches which are arranged on the bag's transverse open edge portion on a first side of the bag. The notches permit holding fingers of a bag clamping device to engage a transverse open edge portion on the interior surface of a bottom or second side of the bag when a suction force is applied to the first side. The bag is opened when the suction force is moved upwardly and the opened bag may then be moved to a vertical position for filling under a spout.
B. Description of the Prior Art
Automatic filling of paper bags is known, and typically takes the form of placing a stack of substantially flat paper bags onto a bag opening machine or magazine. Paper bags used in known automatic processes have gusseted edges and a single notch located on the open transverse edge of the bag's top side. When the paper bags are placed onto the machine in a horizontal position, a bag clamping device consisting of a pivotal holding bar having a finger is placed adjacent to the upper transverse edge. The finger is inserted through the notch for contact against the lower transverse edge of the bag's bottom side. When a suction force is applied to the top side, it is raised and the bottom surface remains substantially flat due to the contacting finger. The gussets, which are accordion or bellowslike in configuration, permit the top side to be raised without also raising the substantially flat configuration of the bottom side. When a predetermined spaced distance between the top and bottom surfaces has been achieved, vertical positioning arms are automatically extended interiorly of the bag for lifting the bag into a vertical open position beneath a filling spout. It is important that the bottom side remain substantially flat so that the vertical positioning arms may be inserted into the bag without damaging contact to the transverse edge portions.
While paper bags have been used extensively in automatic bag opening and filling processes, such bags suffer from certain inherent deficiencies. For instance, paper bags can crack or tear in cold weather and are subject to rot. Paper bags, being air impervious do not "breath" and are hence unsuitable for storing some agricultural products such as potatoes, seed, etc., which require air in order not to spoil. Additionally, paper bags must be of heavy construction in order to hold dairy feed or the like, and even heavy paper material is not rodent proof.
Air pervious bags, such as burlap and polypropylene are strong and suitable for holding feed and various agricultural products but have been heretofore impractical for use in automatic bag opening and filling processes. For instance, burlap sacks or bags are air pervious and permit the lower surface of a horizontally positioned bag to be drawn up with an upper surface when suction is applied to the upper surface. The insertion of vertical positioning arms would thereby be prevented. Also, burlap bags are also sewn or stitched on one edge and hence cannot be adequately placed horizontally flat one on top of another in a bag opening unit.
Furthermore, it has been found economically impractical to form gusseted edges in either burlap sacks or polypropylene bags. Thus, if gusseted edges were not used, as the upper surface is lifted, the bottom surface around its edges also tends to lift with the finger holding down only a small portion of the bag in a relatively flat position. As the upper surface is raised further, it becomes apparent that the vertical positioning arms to be inserted into the bag for vertical placement underneath a spout will contact the edge of the bottom surface and be prevented from insertion into the bag.
With the oil crisis and worldwide inflation, it has also become apparent that burlap bags are rising in cost quite drastically. The main source of burlap bags for American use is India, and procuring such bags at a reasonable cost is becoming increasingly difficult. Therefore, the use of a polypropylene bag is quite desirable but the bag must be so altered to prevent the bottom surface from rising during an automatic opening operation. The present invention describes how a bag may be so constructed.
Polypropylene bags are also desirable because they are rodent resistant, not subject to rot and are air pervious. The present invention enables, for the first time, the automatic opening of a polypropylene bag without impermissible bottom edge distortion by providing multiple notches on a transverse open edge of an upper side. Heretofore, it was considered impossible to adopt polypropylene bags to automatic opening and filling process. Such bags were exclusively manually arranged in an open position underneath a filling spout.